The subject invention relates to brakes, and more particularly to an improved system for power off brakes with manual releases.
Power-off brakes are known in which electrical current to the brake serves to release the brake, which is otherwise activated. Such power-off brakes may be used when it is desirable that the brake be applied in the event of a power failure. For example, an electric wheelchair would desirably be braked in the event of a power failure to prevent accidental movement. However, subsequent movement of the wheelchair is often desired even though the power is off. Hence, there is a need to have the ability to manually release the power-off brake. U.S. Pat. No. 5,915,507 issued Jun. 29, 1999, which is incorporated herein by reference in its entirety, discloses a power-off brake with manual release. Further exemplary brake and brake-related patents include U.S. Pat. No. 6,161,659, issued Dec. 19, 2000; U.S. Pat. No. 6,125,975, issued Oct. 3, 2000; U.S. Pat. No. 5,979,630, issued Nov. 9, 1999; and U.S. Pat. No. 6,047,805, issued May 11, 2000, each of which is incorporated by reference herein in its entirety. Still further exemplary brake and brake-related patent applications include commonly assigned U.S. patent application Ser. No. 09/528,690, filed Mar. 20, 2000; U.S. patent application Ser. No. 09/841,507 filed Sep. 2, 2001; and U.S. patent application Ser. No. 09/773,722 filed Jan. 31, 2001, each of which is incorporated by reference herein in its entirety.
There are problems associated with prior art manual release brake mechanisms. Although they recognize the need to alleviate close manufacturing tolerances, and minimize the effects of wear, binding and/or poor release, each of these problems remains prevalent. There is a need, therefore, for an improved manual release mechanism which permits easy operation and assures adequate performance.
It is an object of the present disclosure to provide a manual release brake mechanism which provides flexible contact to thereby reduce the need for exact manufacturing tolerances and which will minimize component wear.
It is another object of the present disclosure to provide a manual release mechanism which generates a substantial amount of release pressure compared to the effort required to actuate the mechanism.
In one embodiment, a brake includes a manual release mechanism. The manual release mechanism has a lever arm for engaging a reaction plate wherein the rotational motion of the lever is translated into axial motion of the reaction plate which then compresses a bias element. The compression of the bias element generates a manual release force which opposes a braking force generated against a brake element by brake springs. When the manual release force overcomes the braking force, the brake element moves toward the lever arm to disengage the brake.